1. Field of the Invention
This invention relates to electroless metal plating of aramid fibrids, and of papers and sheets containing aramid fibrids, wherein the metal is strongly adhered to the fibrid and provides a highly conductive surface. The aramid fibrids are subjected to a preplating treatment including carefully controlled exposure to a concentrated sulfuric acid solution, followed by washing, and the electroless plating, itself.
2. Description of the Prior Art
Electroless plating is the deposition of a metal film by interaction of metal ions and a chemical reducing agent in a basic solution. Electroless plating, in a general way, is well known. One of the difficulties in achieving successful electroless plating has resided in obtaining good adhesion between the plating substrate and the plated metal. While mere encapsulation may suffice for some applications and some articles, good adhesion of the plated metal is essential for most uses. In the present invention, the plated metal coating on sheets and the materials used to make sheets must be durable enough to withstand the forces of further processing and end use stresses.
Aramid fibers in the form of staple, floc, pulp, and the like and aramid fibrids are known to be useful in constructing sheets and papers. Electroless plating of such materials has, in the past, resulted in metal coatings which exhibited poor adhesion between the surface of the material and the metal.